The present invention relates to a resin curing method for curing resins rapidly by means of energy radiation such as ultraviolet radiation (UV), electron beam (EB), infrared radiation, X-rays, visible light, light from lasers (e.g., argon, CO2 and excimer lasers), sunlight and radiated heat rays, and other energy such as heat, and to polymerization initiators and compositions which enable resins to be cured by this method, molded articles made therefrom, and their production methods and apparatus.
More particularly, the present invention relates to a resin curing method for thick-walled resins in which energy radiation is attenuated or absorbed by the resin to cause a marked reduction in curing action and, therefore, the deep part thereof cannot be cured, and for resins reinforced with fillers (e.g., carbon fiber, metallic fibers and glass fiber) or metallic inserts in which energy radiation is screened by such reinforcing materials and, therefore, the shaded part of the resin cannot be completely cured, and to polymerization initiators and compositions which enable such resins to be cured by this method, molded articles made therefrom, and their production methods and apparatus.
The present invention also relates to a novel resin curing method which enables the energy radiation curing of resin systems containing substances highly capable of screening radiation energy (e.g., carbon, carbon fiber (CF), metals and other inorganic fillers), such as carbon fiber-reinforced composite materials (CFRPS) and carbon/metal/inorganic matter-containing resins, and to compositions therefor, molded articles made therefrom, and their production methods.
The present invention also relates to a method of making a fiber-reinforced composite material (FRP) wherein a composition capable of inducing the novel resin curing mechanism in the aforesaid resin curing method is used as the matrix resin, and a reinforcing fiber (e.g., CF) is impregnated with this resin and then cured by means of energy radiation typified by UV.
The aforesaid curing method, compositions, molded articles and molding methods are effective without regard to the UV screening properties of fibers or fillers, and the length, size and shape thereof. Moreover, they can be utilized not only in the field of composite materials, but also in the fields of adhesives, sealers, varnishes, paints, coating materials, inks, toners and the like.
In recent years, energy radiation-curable resins typified by UV-curable resins are being used in various fields and applications. These resins are characterized in that they are cured only in regions exposed to more than a certain amount of energy radiation. On the other hand, energy radiation typified by UV radiation is characterized in that it is attenuated while it passes through a resin. As a result, it is difficult for energy radiation to reach the deep part of a resin, or energy radiation is greatly attenuated or absorbed, for example, in the presence of a substance capable of absorbing a wavelength equal to that of the energy radiation. Thus, photo-curable resins are cured only in a surface layer having a thickness of several micrometers to several millimeters through which energy radiation can pass, and the deep part thereof remain uncured. Consequently, it is difficult or impossible to apply photo-curable resins to thick-walled materials. Moreover, in the case of resins containing fillers and other substances hindering the passage of energy radiation, they tend to undergo inhibition of their cure and hence become incurable. Owing to these problems, their application has been chiefly limited to the fields of photoresists, coatings, paints, adhesives, varnishes and the like.
Typical solutions to these problems are offered by highly UV-curable resins (Mitsubishi Rayon Co., Ltd.; active energy radiation-curable compositions; Japanese Patent Provisional Publication No. 8-283388/""96) and UV- and heat-cocurable resins {Optomer KS series (Asahi Denka Kogyo K.K.); Radicure (Hitachi Chemical Co., Ltd.); UE resin (Toyobo Co., Ltd.); Japanese Patent Publication (JP-A) No. 6-38023/""86; and the like}. However, highly UV-curable resins still have the problem that they cannot be cured when energy radiation is blocked by a filler or the like. Moreover, in UV- and heat-cocurable resins which are cured by heating after exposure to UV radiation, their energy radiation curability is similar to that of conventional photo-curable resins, and the problems associated with the curing of thick-walled resins and filler-containing resins remain entirely unsolved. Thus, under the existing circumstances, these problems cannot be solved and are hence coped with by heat curing subsequent to photo-curing (of a surface layer alone).
If a technique by which the above-described thick-walled resins containing an energy radiation screening substance or highly capable of attenuating or absorbing energy radiation can be cured rapidly is established, this technique may be applied not only to conventional fields of application, but also to various other fields in which the application of energy radiation curing has been impossible owing to the problems of photo-curable resins. One example thereof is application to the matrix resins of FRPs, particularly CFRPs.
Conventionally, a variety of processing techniques and production processes are employed for FRPs, but the matrix resin consists of a thermosetting or thermoplastic resin in most cases. The problems associated with the molding of FRPs, particularly CFRPs, are that high processing costs are involved because a long curing time results from complicated temperature control, a large-sized heating oven is required for the curing of large-sized FRPs, resins capable of being cured at room temperature in a short period of time cannot be used for large-sized FRPs requiring a long curing time, the molding of FRPs is difficult because the resin-impregnated state varies according to changes in resin viscosity with temperature, and the formation of voids arises from residual solvent during the curing of the resin and causes a reduction in the quality of the molded article.
Recently, as a solution to these problems, the utilization of a photo-curable resin as the matrix resin is attracting attention. A particular and typical example of this matrix resin curing method is the filament winding molding process of Loctite Corp. which uses a combination of UV curing and heat curing (Loctite Corp.; Fiber/resin composition and its preparation method; Published Japanese Translation of PCT International Publication No. 7-507836/""95). However, in the FRP molding process using such a composition, an uncured resin-impregnated FRP is irradiated with UV radiation so as to cure its surface and so as thicken (or gelatinize) its inner part extremely and thereby enable the maintenance of its shape and resin-impregnated state to some extent, and then heated to achieve a complete cure. Accordingly, as compared with the conventional production process using a thermoplastic or thermosetting resin, the change in resin viscosity with temperature is very slight and the handling of the FRP after resin impregnation is easy, but a heat curing step is still required in order to achieve a complete cure. Thus, the problem of high processing costs arising from the fuel and light expenses and operating time required for heat curing, the problem of a long curing time, and the need for a large-sized heating oven in the molding of large-sized FRPs remain unsolved.
In view of the above-described disadvantages of conventional resins cured by energy radiation and the above-described disadvantages of FRPs, particularly CFRPs, the present inventors made intensive investigations on the energy radiation curing of thick-walled resins containing an energy radiation screening substance (i.e., a substance capable of screening energy radiation) and the energy radiation curing of FRPs, particularly CFRPs, and have now attained the present invention. An object of the present invention is to provide a novel resin curing method which enables the energy radiation curing of resin systems containing substances highly capable of screening energy radiation {e.g., carbon, carbon fiber (CF), metals and other inorganic fillers}, such as carbon fiber-reinforced composite materials (CFRPs) and carbon/metal/inorganic matter-containing resins, as well as compositions therefor, molded articles made therefrom, and molding methods thereof.
Another object of the present invention is to incorporate a specific photopolymerization initiator (reaction catalyst system) comprising at least two components (i.e., a system comprising two or more components) into a resin composition highly capable of screening energy radiation, such as a carbon fiber-reinforced composite material (CFRP), whereby even the shaded part or deep part of the resin composition can be completely cured solely by exposure to energy radiation such as UV or EB.
The above objects can be effectively accomplished by various inventions summarized below.
(1) A resin curing method wherein, when energy is applied to a resin composition, another kind of energy than the energy from an external energy source is autogenously generated within the resin, so that the resin composition is cured by means of the autogenously generated energy, or both the autogenously generated energy and the energy from the external energy source.
(2) A resin curing method wherein, when energy is applied to a resin composition, another kind of first energy than the energy from an external energy source is autogenously generated within the resin, and the same kind of second energy is successively generated by the autogenously generated energy, so that the resin composition is cured by means of the first and second energies, or both the first and second energies and the energy from the external energy source.
(3) A resin curing method wherein, when a resin composition is exposed to energy radiation, another kind of energy than the energy from an external energy radiation source is autogenously generated within the resin, so that the resin composition is cured by means of the autogenously generated energy, or both the autogenously generated energy and the energy from the external energy radiation source.
(4) A resin curing method wherein, when a resin composition is exposed to energy radiation, another kind of first energy than the energy from an external energy radiation source is autogenously generated within the resin, and the same kind of second energy is successively generated by the autogenously generated energy, so that the resin composition is cured by means of the first and second energies, or both the first and second energies and the energy from the external energy radiation source.
(5) A resin curing method wherein heat energy is autogenously generated within the resin as the generated energy described above in (3), so that the resin composition is cured by means of the heat energy, or both the heat energy and the energy from the external energy radiation source, whether or not the resin composition contains a substance capable of screening energy radiation (hereinafter referred to as xe2x80x9can energy radiation screening substancexe2x80x9d).
(6) A resin curing method wherein a first heat energy is autogenously generated within the resin as the generated energy described above in (4), and a second heat energy is successively generated by the generated first heat energy, so that the resin composition is cured by means of the first and second heat energies, or both the first and second heat energies and the energy from the external energy radiation source, whether or not the resin composition contains an energy radiation screening substance.
(7) A resin curing method wherein the heat of curing reaction evolved during the cure of the resin composition by exposure to external energy radiation is positively generated as the heat energy autogenously generated within the resin as described above in (5), so that the resin composition is cured by means of the reaction heat energy, or both the reaction heat energy and the energy from the external energy radiation source, whether or not the resin composition contains an energy radiation screening substance.
(8) A resin curing method wherein the heat of curing reaction evolved during the cure of the resin composition by exposure to energy radiation is positively generated as the first heat energy autogenously generated within the resin as described above in (6), and the curing reaction is further effected, like a chain reaction, by the action of the heat of curing reaction to generate additional heat of curing reaction as the successively generated second heat energy, so that the resin composition is cured by means of the first and second reaction heat energies, or both the first and second reaction heat energies and the energy from the energy radiation source, whether or not the resin composition contains an energy radiation screening substance.
(9) A resin curing method wherein, in the curing reaction described above in any of (1) to (8), at least one species selected from the group consisting of a cation, a radical and an anion is utilized to induce curing or facilitate the curing reaction by the action of the energy from the external energy source, the energy radiation from the energy radiation source, or the heat of reaction.
(10) A resin curing method as described above in (9) wherein, when the resin composition is exposed to energy radiation, a cation and a first heat of curing reaction evolved during the cure of the resin composition by the action of the energy radiation are positively generated within the resin, and the curing reaction is further effected, like a chain reaction, by the action of the cation and the first heat of curing reaction to successively generate an additional cation and a second heat of curing reaction, so that the resin composition is cured by means of the first and second reaction heat energies and the cation, or the combination of the first and second reaction heat energies, the cation, and the energy from the energy radiation source, whether or not the resin composition contains an energy radiation screening substance.
(11) A resin curing method as described above in any of (1) to (10) wherein the cure of the resin composition is facilitated by warming it previously in a temperature range which does not cause its cure.
(12) A resin curing method as described above in any of (1) to (11) wherein a polymerization initiator is used.
(13) A resin curing method as described above in any of (1) to (12) wherein the cure of the composition is initiated by means of heat or the composition is cured by means of heat.
(14) A photopolymerization initiator comprising at least two components including a photopolymerization initiator and a photo- and thermopolymerization initiator for initiating polymerization by means of both light and heat, and serving as the polymerization initiator making it possible to carry out a resin curing method as described above in (13).
(15) A photopolymerization initiator comprising at least two components as described above in (14) wherein a photo- and thermopolymerization initiator having a powerful polymerization-initiating effect upon exposure to heat is used as the photo- and thermopolymerization initiator.
(16) A photopolymerization initiator comprising at least two components which includes at least one photopolymerization initiator comprising at least two components as described above in (14) or (15), and a thermopolymerization initiator.
(17) A photopolymerization initiator comprising at least two components as described above in any of (14) to (16) which consists essentially or entirely of radical polymerization initiators.
(18) A photopolymerization initiator comprising at least two components as described above in any of (14) to (16) which consists essentially or entirely of anionic polymerization initiators.
(19) A photopolymerization initiator comprising at least two components as described above in any of (14) to (16) which consists essentially or entirely of cationic polymerization initiators.
(20) A photopolymerization initiator comprising at least two components as described above in (19) wherein the photopolymerization initiator comprises at least one compound selected from diazonium salt type compounds, iodonium salt type compounds, pyridinium salt type compounds, phosphonium salt type compounds, sulfonium salt type compounds, iron-arene complex type compounds, and sulfonate type compounds, and the photo- and thermopolymerization initiator comprises at least one of the sulfonium salts represented by the following general formulae (I), (II), (III), (IV), (V), (VI) and (VII). 
where R1 represents hydrogen, methyl, acetyl or methoxycarbonyl, R2 and R3 each independently represents hydrogen, halogen or an alkyl group of 1 to 4 carbon atoms, R4 represents hydrogen, halogen or methoxy, R5 represents an alkyl group of 1 to 4 carbon atoms, and A represents SbF6, PF6, AsF6 or BF4. 
where R6 represents a hydrogen atom, a halogen atom, a nitro group or a methyl group, R1 represents a hydrogen atom, CH3CO or CH3OCO, and A represents SbF6, PF6, BF6 or AsF6. 
where R8 represents a hydrogen atom, CH3CO or CH3OCO, and A represents SbF6, PF6, BF6, AsF6 or CH3SO4. 
where X represents a sulfonio group of the general formula 
in which R9 represents an aliphatic group of 1 to 18 carbon atoms, R10 represents an aliphatic group of 1 to 18 carbon atoms or a substituted or unsubstituted aromatic group of 6 to 18 carbon atoms, and R9 and R10 may be joined together to form a ring; Y represents a sulfonio group of the general formula 
in which R11 represents an aliphatic group of 1 to 18 carbon atoms, R12 represents an aliphatic group of 1 to 18 carbon atoms or a substituted or unsubstituted aromatic group of 6 to 18 carbon atoms, and R11 and R12 may be joined together to form a ring, or Y represents a hydrogen a hydrogen atom, a halogen atom, a nitro group, an alkoxy group, an aliphatic group of 1 to 18 carbon atoms, or a substituted or unsubstituted phenyl, phenoxy or thiophenoxy group of 6 to 18 carbon atoms; n and m are each independently 1 or 2; and Z is an anion represented by the formula MQ1 or MQ1xe2x80x941OH in which M is B, P, As or Sb, Q is a halogen atom, and 1 is 4 or 6. 
where R13 and R14 independently represent hydrogen or alkyl groups of 1 to 4 carbon atoms, and A represents SbF6, PF6 or ASF6 . 
where R15 represents ethoxy, phenyl, phenoxy, benzyloxy, chloromethyl, dichloromethyl, trichloromethyl or trifluoromethyl, R16 and R17 each independently represents hydrogen, halogen or an alkyl group of 1 to 4 carbon atoms, R18 represents hydrogen, methyl, methoxy or halogen, R19 represents hydrogen, methyl, methoxy or halogen, R19 represents an alkyl group of 1 to 4 carbon atoms, and A represents SbF6, PF6, BF4 or AsF6. 
where Q represents methoxycarbonyloxy, acetoxy, benzyloxycarbonyloxy or dimethylamino, R20 and R21 each independently represents hydrogen or an alkyl group of 1 to 4 carbon atoms, R22 and R23 each independently represents an alkyl group of 1 to 4 carbon atoms, and A represents SbF6, PF6, AsF6 or BF4.
(21) A photopolymerization initiator comprising at least two components as described above in (20) wherein the photopolymerization initiator comprises an arylsulfonium salt type compound, and the photo- and thermopolymerization initiator comprises at least one sulfonium salt represented by the general formula (I), (II) or (III).
(22) A photopolymerization initiator comprising at least two components which includes at least one of the photopolymerization initiator comprising at least two components as described above in any of (19) to (21), and a thermopolymerization initiator comprising at least one of the compounds represented by the following chemical formulae (VIII) and (IX). 
(23) A composition making it possible of carry out a curing method as described above in any of (1) to (13) wherein, when the composition is exposed to energy radiation, another kind of energy than the energy from the energy radiation source is autogenously generated within the composition, or wherein, when the composition is exposed to the energy radiation, another kind of first energy than the energy from the energy radiation source is autogenously generated within the composition, and the same kind of second energy is successively generated by the generated first energy.
(24) A composition as described above in (23) which contains a photopolymerization initiator and a photopolymerizable oligomer or photopolymerizable monomer.
(25) A composition as described above in (23) or (24) which contains, as an essential ingredient, a photopolymerization initiator comprising at least two components as described above in any of (14) to (22).
(26) A resin composition as described above in (25) which comprises, as essential ingredients, any of the photopolymerization initiators comprising at least two components as described above in any of (19) to (22), and a cationic photopolymerizable oligomer or cationic photopolymerizable monomer.
(27) A resin composition as described above in (26) wherein a photbpolymerizable epoxy oligomer or photopolymerizable epoxy monomer is used as the cationic photopolymerizable oligomer or cationic photopolymerizable monomer.
(28) A resin composition as described above in (27) wherein a photopolymerizable alicyclic epoxy oligomer or photopolymerizable alicyclic epoxy monomer is used as the photopolymerizable epoxy oligomer or photopolymerizable epoxy monomer.
(29) A resin composition as described above in (28) wherein 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate is used as the photopolymerizable alicyclic epoxy monomer.
(30) A resin composition as described above in any of (25) to (29) wherein the photopolymerization initiator comprising at least two components is contained in an amount of 0.5 to 6.0 parts by weight per 100 parts by weight of the photopolymerizable resin component (photopolymerizable oligomer or monomer), and the weight ratio of the photo- and thermopolymerization initiator to the photopolymerization initiator constituting the photopolymerization initiator comprising at least two components is in the range of 1 to 4.
(31) A resin composition as described above in (30) which comprises a photopolymerization initiator comprising at least two components as described above in any of (20) to (22), and a photopolymerizable resin component as described above in any of (26) to (29).
(32) A composition as described above in any of (23) to (31) which contains at least one additive selected from energy radiation screening substances, various fillers and organic components.
(33) A composition as described above in any of (23) to (32) which additionally contains at least one additive selected from photosensitizers, reactive diluents and photosensitive compounds.
(34) A cured product obtained by a method as described above in any of (1) to (13).
(35) A molded article made from a composition containing a photopolymerization initiator comprising at least two components as described above in any of (4) to (22).
(36) A molded article made from a composition as described above in any of (23) to (33).
(37) A molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material, other composite material, adhesive, sealer, varnish, paint or coating material, ink or toner which contains a composition making it possible to carry out a resin curing method as described above in any of (1) to (13).
(38) A molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material, other composite material, adhesive, sealer, varnish, paint or coating material, ink or toner which contains a photopolymerization initiator comprising at least two components as described above in any of (14) to (22).
(39) A molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material, other composite material, adhesive, sealer, varnish, paint or coating material, ink or toner which contains a composition as described above in any of (23) to (33).
(40) A method of making a molded article of a molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material or other composite material, a cured product of an adhesive, sealer, varnish, paint or coating material, or matter printed with ink or toner, by utilizing a resin curing method as described above in any of (1) to (13).
(41) A method of making a molded article of a molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material or other composite material, a cured product of an adhesive, sealer, varnish, paint or coating material, or matter printed with ink or toner, by utilizing a resin composition making it possible to carry out a curing method as described above in any of (1) to (13).
(42) A method of making a molded article of a molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material or other composite material, a cured product of an adhesive, sealer, varnish, paint or coating material, or matter printed with ink or toner, by utilizing a composition containing a photopolymerization initiator comprising at least two components as described above in any of (14) to (22).
(43) A method of making a molded article of a molding material, fiber-reinforced composite material, carbon fiber-reinforced composite material or other composite material, a cured product of an adhesive, sealer, varnish, paint or coating material, or matter printed with ink or toner, by utilizing a resin composition as described above in any of (23) to (33).
(44) A method of making a fiber-reinforced composite material or carbon fiber-reinforced composite material as described above in any of (40) to (43) wherein the fiber-reinforced composite material or carbon fiber-reinforced composite material is made by utilizing at least one technique selected from hand lay-up, spray-up, filament winding, tape winding, roll winding, draw molding and continuous roll pressing.
(45) A method of making a prepreg which comprises impregnating a reinforcing fiber or a reinforcing fiber cloth material with a resin composition as described above in any of (23) to (33).
(46) A method of making a fiber-reinforced composite material which comprises stacking prepregs made by the method described above in (45), and curing them according to a curing method as described above in any of (1) to (13).
(47) A method of making a fiber-reinforced composite material which comprises impregnating a three-dimensional textile with a composition as described above in any of (23) to (33), and curing it according to a curing method as described above in any of (1) to (13).
(48) A method of repairing a fiber-reinforced composite material, building, structure or product which comprises filling a part to be repaired of a fiber-reinforced composite material, building, structure or product with a composition as described above in any of (23) to (33), or attaching a prepreg made by the method described above in (45) to a part to be repaired of a fiber-reinforced composite material, building, structure or product; and curing the composition or prepreg according to a curing method as described above in any of (1) to (13).
(49) A method of reinforcing a fiber-reinforced composite material, building, structure or product which comprises attaching a prepreg made by the method described above in (45) to a part to be reinforced of a fiber-reinforced composite material, building, structure or product, and curing the prepreg according to a curing method as described above in any of (1) to (13), or which comprises using a composition as described above in any of (23) to (33), attaching a reinforcing fiber or reinforcing fiber cloth material to a part to be reinforced of a fiber-reinforced composite material, building, structure or product by spray-up or brushing, and curing the composition according to a curing method as described above in any of (1) to (13)
(50) A method as described above in any of (40) to (49) wherein carbon fiber is used as the fibrous material.
(51) A method as described above in any of (40) to (50) wherein there is used a material in which the composition contains a photopolymerization initiator comprising at least two components as described above in any of (20) to (22).
(52) A method as described above in any of (40) to (50) wherein there is used a material comprising a composition as described above in (30).
(53) A method as described above in any of (40) to (50) wherein there is used a composition as described above in (31).
(54) A molded article made by a method as described above in any of (40) to (43).
(55) A fiber-reinforced composite material or carbon fiber-reinforced composite material as described above in any of (37) to (39).
(56) A molded article made by the method described above in (44).
(57) A prepreg made by the method described above in (45).
(58) A fiber-reinforced composite material obtained by curing a prepreg as described above in (57).
(59) A fiber-reinforced composite material obtained by impregnating a three-dimensional textile with a composition as described above in any of (23) to (33), and curing the resin composition.
(60) A repair material for filling a part to be repaired of a fiber-reinforced composite material, building, structure or product which comprises a composition as described above in any of (23) to (33).
(61) A reinforcing material for a fiber-reinforced composite material, building, structure or product which comprises a composition as described above in any of (23) to (33).
(62) A material or molded article as described above in any of (37) to (39) or any of (54) to (61) wherein carbon fiber is used as the fibrous material.
(63) A material or molded article as described above in any of (37) to (39) or any of (54) to (62) wherein the composition contains a photopolymerization initiator comprising at least two components as described above in any of (20) to (22).
(64) A material or molded article as described above in any of (37) to (39) or any of (54) to (62) which comprises a composition as described above in (30).
(65) A material or molded article as described above in any of (36) to (38) or any of (54) to (62) which comprises a composition as described above in (30).
In the above-described methods of the present invention, particularly in the methods described in (1) to (13), the resin composition can be cured by causing energy (e.g., heat energy) to be autogenously generated within the resin and, in some cases, causing energy to be successively generated by the generated energy. Specifically, the above-described methods can be carried out by using, as the polymerization reaction catalyst, a photopolymerization initiator system (reaction catalyst system) comprising at least two components including a photopolymerization initiator and a photo- and thermopolymerization initiator.
That is, to sum up more briefly, the present invention is characterized by a novel resin curing mechanism enabling the energy radiation curing of CFRPs and thick-walled resins containing an energy radiation screening substance, photopolymerization initiator systems (reaction catalyst systems) comprising at least two components and capable of inducing this curing mechanism, and compositions containing them. It is preferable to use a photopolymerization initiator system (reaction catalyst system) comprising at least two components in which the photopolymerization initiator comprises at least one compound selected from diazonium salt type compounds, iodonium salt type compounds, pyridinium salt type compounds, phosphonium salt type compounds, sulfonium salt type compounds, iron-arene complex type compounds and sulfonate type compounds, and the photo- and thermopolymerization initiator comprises at least one of the sulfonium salts represented by the general formulae (I) to (VII). It is more preferable to use a photopolymerization initiator system (reaction catalyst system) comprising at least two components in which the photopolymerization initiator comprises an arylsulfonium type compound (i.e., a triarylsulfonium type compound) and the photo- and thermopolymerization initiator comprises at least one of the sulfonium salts represented by the general formulae (I), (II) and (III).
Moreover, thermopolymerization initiators, typified by those of chemical formulae (VIII) and (IX), may be added to the aforesaid photopolymerization initiator systems comprising at least two components. Furthermore, the present invention also relates to the compositional range of specific photopolymerization initiator systems comprising at least two components; resin compositions capable of inducing the novel resin curing mechanism, the formulations thereof, and molded articles made therefrom; a method for utilizing the aforesaid curing mechanism and resin compositions; and a method of making FRPs using such a resin as the matrix resin, resin compositions therefor, and molded articles made therefrom.